Industry in walrus territory
1 May 2017
Pacific walruses are segregated by gender for much of the year. Adult females and young follow the ice edge as it recedes through the Chukchi Sea in summer and they return to the Bering Sea in winter, while most males stay in the Bering Sea year-round. XAVIER MOUY says studies are underway to assess the effects of industrial activities on walruses.
CLIMATE CHANGE has led to an earlier retreat of sea ice in summer and a later fall return, requiring walruses to change their use of the Chukchi Sea. At the same time, longer open water periods make the region more accessible to human activities. The oil and gas industry has been assessing hydrocarbon prospects in the northeastern Chukchi Sea off Alaska over the past decade. Ship traffic in the Arctic has increased over the years, with growth expected to continue through 2050 when the Arctic Ocean is expected to be largely free of summer sea ice. The effects of reduced sea ice and increased human activity near walrus feeding habitat could be detrimental to these mammals.
Oil and gas activities include seismic surveys that use underwater airguns to generate loud pulses of sound used for mapping hydrocarbon deposits within the sea bottom, and drilling of exploration wells to assess viability of the most promising finds. Both operations generate underwater noise that can affect walruses’ hearing and use of sound. To mitigate such impacts, on-site acoustic measurements are carried out in combination with sound propagation modeling to determine the distances from activities over which harmful noise effects could occur. Marine mammal observers (MMOs) are deployed on most exploration vessels to watch carefully for animals that could approach within marine mammal exclusion or safety zones. MMOs have the authority to halt the noise-generating activities if animals are observed close to the exclusion zone.
From 2006 to 2015, several oil and gas companies performed hydrocarbon exploration in the northeastern Chukchi Sea. Some of these companies funded multidisciplinary long-term environmental projects to collect ecological baseline measurements and to inform regulatory permit applications. The Chukchi Sea Environmental Studies Program (CSESP), the largest of these multiyear studies, included a large passive acoustic monitoring component that enabled scientists to describe seasonal and spatial use of the northeastern Chukchi Sea by walruses, by listening for underwater sounds produced by these highly vocal animals. This study identified important walrus concentrations, or “hotspots”, and quantified the natural and man-made underwater noise levels over a large area of the sea. Such baseline measurements are essential to understand the effects of additional noise from human activities on walruses and to inform planning to mitigate possible impacts; they help industry and regulatory agencies make informed decisions on where and when to operate (i.e. by avoiding loud activities near sensitive walrus habitat when walruses are present).
These large environmental programs have advanced the understanding of the distribution of walruses in the northeastern Chukchi Sea, leading to several peer-reviewed publications in scientific journals and environmental impact assessment reports provided to government agencies. Still, many knowledge gaps remain. While there is some quantitative information available on walrus hearing, the effects of chronic increases in background noise on walrus behavior and communication are poorly understood.
The northeastern Chukchi Sea is an important feeding ground for mothers and calves during the summer months. Sound is an essential tool to them as they vocalize to communicate and keep track of each other. It has been shown that calves can recognize their mothers from their vocalizations alone. Disruption of this communication due to increased noise in the ocean could lead to detrimental effects on the survival of calves and consequently on the walrus population. Noise levels at which such communication disruptions occur are currently unknown. The effects of noise on walruses’ behavior is also poorly understood, and it is currently unknown whether walruses avoid areas with increased noise levels. If they do, industrial noise might deter walruses from prime feeding habitat.
Industry-funded research has furthered knowledge about Pacific walruses in the northeastern Chukchi Sea on a scale that would likely not have happened otherwise. It has filled critical information gaps and provided valuable baseline data that are keystones for quantifying the effects of underwater noise on walruses. Many other pieces of the puzzle are however still missing to fully understand how the walrus population might be affected and what can be done to mitigate adverse effects. Such questions must be addressed before any large scale industrial activities happen in this region of Arctic waters.
XAVIER MOUY is a scientist with the Canadian consulting company JASCO Applied Sciences. He specializes in the passive acoustic monitoring of whales, pinnipeds and fish for numerous environmental impact studies for industry in the U.S. and Canadian Arctic.
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